Adjuvant and immuno-suppressive effect of six monophthalates in a subcutaneous injection model with BALB/c mice

The prevalence of allergic airway diseases is rapidly increasing in Western Europe and North America. This increase in disease prevalence may be associated with environmental pollutants. The present study investigated the adjuvant and immuno-suppressive effect of a series of monophthalates which are considered to be important metabolites of commonly used phthalate plasticizers. The effects were studied in a screening model. Ovalbumin (OA), used as the model antigen, was injected subcutaneously in the neck region of BALB/cJ mice with or without one of the test substances, mono-n-butyl phthalate (MnBP), monobenzyl phthalate (MBnP), mono-n-octyl phthalate (MnOP), mono-2-ethylhexyl phthalate (MEHP), mono-iso-nonyl phthalate (MiNP) or mono-iso-decyl phthalate (MiDP). The levels of OA-specific IgE, IgG1 and IgG2a in sera were measured by ELISA. Immuno-suppressive effect, defined as a statistically significant reduction in IgE or IgG1 antibody production, was observed with MEHP (1000 μg/ml, IgE and IgG1), MnOP (1000 μg/ml, IgE and IgG1), MiNP (1000 μg/ml, IgE and 10 μg/ml, IgG1) and MiDP (100 μg/ml, IgE and IgG1). Adjuvant effect, defined as a statistically significant increase in IgE or IgG1 antibody level, occurred with MEHP (10 μg/ml, IgE), MnOP (100 μg/ml, and 10 μg/ml, IgG1) and MiNP (100 μg/ml, IgE). No statistically significant immune modulating effect was seen with MBnP and MnBP.